Integrated splitter gearbox for four wheel drive tractors

ABSTRACT

A splitter gearbox for a four wheel drive, hydrostatically driven tractor integrates both the input drive train and the output drive train into a single gearbox. The splitter gearbox is mounted to the rear axle housing to allow the sharing of a common oil sump. The front and rear axles of the tractor are driven from a single hydrostatic motor associated with a gear drive system that provides a shaft extending forwardly and rearwardly out of the splitter gearbox to drive, respectively, the front and rear axles of the tractor. An auxiliary pump drive is mounted to the side of the splitter gearbox and driven from an idler gear appropriately positioned within the splitter gearbox.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims domestic priority on U.S. Provisional PatentApplication Ser. No. 60/097,463, filed on Aug. 21, 1998.

BACKGROUND OF THE INVENTION

This invention relates generally to four wheel drive articulatedtractors and, more particularly, to improvements to the drive system forhydrostatically driven tractors.

It is desirable to integrate all the drives for the input drivencomponents of an articulated four wheel drive tractor into a singlegearbox affixed to the rear axle housing of the tractor. Such amechanism would place the hydrostatic pump for powering the tractiondrive of the tractor, the hydraulic pump for the tractor hydraulicsystem, the drive for the power-takeoff (PTO) system, and any auxiliaryhydraulic pumps to be driven off the same gearbox device with the outputdriver components, including the hydrostatic motor, speed reductiongears and output drive shafts.

Lubrication of a gear set is a consideration is the design of a gearboxdevice for transferring rotational power through gear sets arranged andconfigured to provide the proper rotational speed to a component drivenfrom the engine of the tractor. Commonizing lubrication sumps canminimize the number of lubrication systems that need to be provided aswell as provide more effective lubrication of the gear sets and thecooling of the lubrication fluid.

Conventional tractor drive mechanisms include a mechanical transmissionto provide different output speeds for a given engine input speed. Evenhydraulically driven tractors have utilized a three speed mechanicaltransmission between the engine and the hydrostatic pump to providedesired different input speeds to the operation of the hydrostatic pumpfor powering the movement of the tractor. It would be desirable toreplace the three speed mechanical transmission on hydrostaticallydriven tractors to minimize cost and to enhance operation of thetractor.

The gearbox would preferably be configured to mount the auxiliary pumpdrive mechanism in an optional manner so that the auxiliary pump couldbe added to the gearbox, if desired, and be driven therefrom.

SUMMARY OF THE INVENTION

It is an object of this invention to integrate the drive mechanisms fora hydrostatically driven, four wheel drive tractor in which all thedrives are driven from a single splitter gearbox.

It is a feature of this invention that the splitter gearbox is affixedto the rear axle housing of the tractor.

It is an advantage of this invention that the mounting of the splittergearbox to the rear axle housing allows the splitter gearbox and therear axle housing to share a common oil sump.

It is another advantage of this invention that the mounting of thesplitter gearbox to the rear axle housing reduces complexity.

It is another object of this invention to drive the front and rear axlesof a four wheel drive tractor from a variable displacement hydrostaticmotor.

It is another feature of this invention that a hydraulically driventractor need not have a conventional transmission in order to obtaincustomary speed ranges desired for a tractor.

It is still another feature of this invention that the variabledisplacement hydrostatic motor can be provided with a selected number ofpre-set swash plate positions to effectively replace a conventionaltransmission gearbox.

It is another advantage of this invention that the fixed positions ofthe variable displacement hydrostatic motor, coupled with a variablespeed hydraulic pump, can be controlled electronically to provide asmooth power-shifting operation.

It is still another advantage of this invention that the tractor doesnot require stopping to shift gears in order to change the range ofoperation of the tractor.

It is another feature of this invention that the splitter gearboxincorporates a gear drive system in association with the hydrostaticmotor to provide a shaft extending forwardly and rearwardly out of thesplitter gearbox to drive, respectively, the front and rear axles of thetractor.

It is still another advantage of this invention that the front and rearaxles of the four wheel drive tractor are driven from a singlehydrostatic motor.

It is still another object of this invention that the input drive trainand the output drive train arc incorporated into a single splittergearbox.

It is yet another object of this invention to provide an auxiliary pumpdrive for a four wheel drive tractor.

It is still another feature of this invention that the auxiliary pumpdrive can be mounted as an option to the side of the splitter gearbox.

It is yet another advantage of this invention that the auxiliary pumpcan be driven from an idler gear appropriately positioned within thesplitter gearbox.

It is a further object of this invention to provide a splitter gearboxfor a four wheel drive, hydrostatically driven tractor which is durablein construction, inexpensive of manufacture, carefree of maintenance,facile in assemblage, and simple and effective in use.

It is still a further object of this invention to provide an auxiliarydrive mechanism that can be mounted on a splitter gearbox for a fourwheel drive, hydrostatically driven tractor, which is durable inconstruction, inexpensive of manufacture, carefree of maintenance,facile in assemblage, and simple and effective in use.

These and other objects, features, and advantages are accomplishedaccording to the instant invention by providing a splitter gearbox for afour wheel drive, hydrostatically driven tractor in which the inputdrive train and the output drive train are integrated into a singlegearbox. The drive mechanism eliminates the need for a separatemechanical gearbox by establishing pre-set fixed displacement settingsthat are electronically controlled along with the variable displacementof the hydrostatic motor and hydrostatic pump, to provide a smooth powershift through all ranges without requiring the tractor to stop. Thedrive mechanism is configured so that essentially all components areindividually controlled so that the entire power generated by thetractor engine can be diverted to any one of the traction drive, the PTOmechanism, the auxiliary hydraulic drive or, to a somewhat lesserextent, the tractor hydraulic system. The splitter gearbox is mounted tothe rear axle housing to allow the sharing of a common oil sump. Theinput gear set and the output gear set are also within the same commonlubrication sump within the splitter gearbox.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of this invention will become apparent upon considerationof the following detailed disclosure of the invention, especially whentaken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevational view of a four wheel drive, articulatedtractor incorporating the principles of the instant invention, portionsof the tractor being broken away for purposes of clarity;

FIG. 2 is a schematic side elevational view of the drive mechanismhaving a splitter gearbox and associated drives incorporating theprinciples of the instant invention;

FIG. 3 is a top plan view of the splitter gearbox and rear axle housingcorresponding to lines 3—3 of FIG. 2;

FIG. 4 is a front elevational view of the splitter gearbox andassociated drives corresponding to lines 4—4FIG. 3;

FIG. 5 is a rear elevational view of the splitter gearbox correspondingto lines 5—5 of FIG. 3;

FIG. 6 is a cross-sectional view through the splitter gearbox takenalong lines 6—6 of FIG. 3;

FIG. 7 is a cross-sectional view of the splitter gearbox taken alonglines 7—7 of FIG. 6 to depict the gear drive system for driving thefront and rear axles from a single hydrostatic motor shown in phantom;

FIG. 8 is a cross-sectional view of the splitter gearbox similar to thatof FIG. 6 to depict the addition of an optional auxiliary pumpmechanism; and

FIG. 9 is a top plan view of the splitter gearbox and rear axle housingsimilar to that of FIG. 3 but with an optional auxiliary hydraulic pumpmounted to the splitter gearbox.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, a four wheel drive, articulated tractorincorporating the principles of the instant invention can best be seen.The articulated tractor 10 includes a forward engine end 11 supportedabove the ground G by a front axle assembly 12 and carrying an engine13. The rearward cab end 16 of the tractor 10 is supported above theground by a rear axle assembly 17 and has an operator's station 18mounted thereon. Each of the front and rear axle assemblies 12, 17 isprovided with a pair of opposing wheels 19 for mobile movement of thetractor 10 over the surface of the ground G. The front and rear ends 11,16 of the tractor 10 arc connected by an articulation joint 15, themanipulation of which effects steering of the tractor 10 in a knownmanner.

As best seen in FIGS. 1-7, the tractor 10 is provided with a drivesystem 20 that is operatively connected to the engine 13 to provideoperative power for the front and rear axle assemblies 12, 17. The drivesystem 20 includes a splitter gearbox 30 mounted on the front of therear axle assembly 17 in a manner to share the oil sump therewith forlubrication purposes. The drive system 20 also includes the input drivecomponents, including a hydrostatic pump 22 for powering the tractiondrive of the tractor 10, a hydraulic pump 24 for pressuring thehydraulic system of the tractor 10, and a power takeoff (PTO) mechanism29; and the output drive components, including a variable displacementhydrostatic motor 25 to provide operative power to both the front andrear axle assemblies 12, 17 through front and rear output drive shafts26, 27.

The splitter gearbox 30 receives rotational power from the engine 13 viaa power input shaft 31 interconnecting the engine 13 and the splittergearbox 30 to rotate the input gear 32. As best seen in FIGS. 4-6, theinput gear 32 is drivingly engaged with a first idler drive gear 33, thesize of the respective gears 32, 33 being selected to provide theappropriately desired gear reduction. The first idler drive gear 33 isdrivingly engaged with a pump drive gear 34 having both the hydrostaticpump 22 and the hydraulic pump 24 coaxially mounted therewith, thehydrostatic pump 22 being mounted on the front of the splitter gearbox30 and the hydraulic pump 24 being mounted on the rear of the splittergearbox 30. The idler drive gear 33 is also drivingly engaged with thePTO drive gear 39 for powering the PTO mechanism 29 as a direct driveinput from the engine 13.

As best seen in FIGS. 3-7, the hydrostatic pump 22 is operable tocirculate hydraulic fluid under pressure to a variable displacementhydraulic motor 25 mounted on the front of the splitter gearbox 30 belowthe hydrostatic pump 22 to drive rotation of the hydraulic motor 25. Thedrive pinion 35 of the hydrostatic motor 25 is drivingly engaged with asecond idler gear 36, which is also appropriately sized to provide thedesired gear reduction. The second idler gear 36 is drivingly engagedwith a traction driven gear 37 having a single shaft 38 extendingtherethrough to project both forwardly and rearwardly from the splittergearbox 30 and form the front and rear output drive shafts 26, 27.Control of the hydrostatic pump is effected through a conventionalmechanical linkage.

The hydrostatic motor 25 is preferably set-up with three pre-set, fixedswash plate angles to provide three positive displacements for the motor25 to proximate a conventional operation of the tractor 10. By utilizingthe variable displacement of the hydrostatic motor 25 and/or a variablespeed hydrostatic pump 22, the infinite speed adjustment for the tractor10 can still be attained on-the-go. Using an electronic control systemto control the operation of the motor 25, such as by modulating thedisplacement of the motor 25, and to control the operation of the pump22, a very smoothly operating power-shift tractor 10 will result withoutrequiring the operator to stop the tractor to change gears in amechanical transmission, as is conventional. The fixed, pre-setdisplacements for the hydrostatic motor 25 provide maximum torque andminimum speed at a first position, a mid-range of both torque and speedat a second position, and a minimum torque with maximum speed forroading operations at a third position.

As best seen in FIGS. 1 and 2, the front axle assembly 12 is drivinglyconnected to the front output drive shaft 26 by a front drive shaftassembly 26 a. The rear axle assembly 17 is drivingly connected to therear output drive shaft 27 by a rear drive shaft assembly 27 a passinginternally through the housing 28 of the rear axle assembly 17.Likewise, the PTO mechanism 29 is drivingly connected to the PTO drivegear 39 and passes through the housing 28 of the rear axle assembly 17and projects rearwardly therefrom for remote connection to an apparatus(not shown) for delivering rotational power thereto.

Accordingly, the top portion of the splitter gearbox 30 receivesrotational power directly from the engine 13 and drives the input drivetrain components, including the hydrostatic pump 22, the hydraulic pump24 and the PTO mechanism 29. The lower portion of the splitter gearbox30 receives operative power from the hydrostatic motor 25 operativelydriven from the hydrostatic pump 22 and delivers the rotational powerthrough the output shafts 26, 27 to drive the front and rear axleassemblies 12, 17 from a single hydrostatic motor 25 off of a singlegear drive set 35-37.

Referring now to FIGS. 8 and 9, the configuration of the splittergearbox 30 to receive an optional, auxiliary hydraulic assembly 40,which includes an auxiliary pump 41, having a drive pinion 42, and arotatably mounted third idler gear 43 drivingly engaged with the drivepinion 42. The third idler gear 43 projects outwardly from the housing44 of the auxiliary hydraulic assembly 40 such that the mounting of thehousing 44 to the side of the splitter gearbox 30, as described ingreater detail below, will cause the third idler gear 43 to becomedrivingly engaged with the input gear 32 and, thereby, drive theoperation of the auxiliary pump 41, which can then supplement tooperation of the primary hydraulic pump 24.

The process for installing the auxiliary hydraulic assembly 40 is bestseen in FIG. 8. First the removable side cover 45 of the splittergearbox 30 is detached from the splitter gearbox 30. The auxiliaryhydraulic assembly 40 is then positioned such that the third idler gear43 extends into the opening in the side of the splitter gearbox 30formed with the removal of the side cover 45 and becomes engaged withthe input gear 32 to receive rotational power directly from the engine13, as is the primary hydraulic pump 24. The housing 44 is then boltedinto place on the side of the splitter gearbox and sealed thereto as areplacement for the side cover 45.

The splitter gearbox configuration described above provides a number ofdifferent operational configurations for the operator of thishydrstatically driven tractor 10. By disengaging all other outputcomponents, the operator can choose to direct the entire power of theengine 13 to the hydrostatic motor 25 to provide for maximum speedand/or pulling torque of the tractor 10 through one of the pre-set fixedpositions of the motor 25. Alternatively, the operator could disengagethe hydrostatic motor 25 by placing its swash plate in a neutralposition and run the entire power of the engine 13 through the PTO shaft29, while the tractor 10 remains stationary. Another alternative for theoperator, would be to disengage both the hydrostatic motor 25 and thePTO mechanism 29, and run the entire power of the engine 13 through theauxiliary hydraulic system 40. Yet another alternative for the operatorwould be to disengage all of the hydrostatic motor 25, the PTO mechanism29, and the auxiliary hydraulic system 40 (if the tractor 10 is soequipped), and divert as much of the power from the engine as possiblethrough the tractor hydraulic system through the hydraulic pump 24;however, since both the hydrostatic pump 22 and the hydraulic pump 24are run from the same gear 34, less than full engine power can be runthrough the tractor hydraulics. One skilled in the art will readilyrecognize that a combination of the above systems will typically beoperated, and the operator will have appropriate choices to make forapplication of the power from the engine 13.

It will be understood that changes in the details, materials, steps andarrangements of parts which have been described and illustrated toexplain the nature of the invention will occur to and may be made bythose skilled in the art upon a reading of this disclosure within theprinciples and scope of the invention. The foregoing descriptionillustrates the preferred embodiment of the invention; however,concepts, as based upon the description, may be employed in otherembodiments without departing from the scope of the invention.Accordingly, the following claims are intended to protect the inventionbroadly as well as in the specific form shown.

Having thus described the invention, what is claimed is:
 1. In a tractorhaving a chassis supported by a front axle assembly and a rear axleassembly, and an engine for providing operative power, an improved drivemechanism comprising: a splitter gearbox mounted to the rear axleassembly to share a common oil sump therewith, said splitter gearboxbeing operatively connected to said engine to receive rotational powertherefrom and being operatively connected to said front and rear axleassemblies to deliver rotational power thereto, said splitter gearboxhas supported therefrom and provides operative power to a hydrostaticpump providing traction power for powering the front and rear axleassemblies, a hydraulic pump providing hydraulic fluid under pressure toa hydraulic system on said tractor and a power takeoff mechanism.
 2. Thetractor of claim 1 wherein said splitter gearbox further supports ahydrostatic motor and output drives interconnecting said splittergearbox and said front and rear axle assemblies to provide tractionpower thereto, said hydrostatic motor being operatively connected tosaid hydrostatic pump to receive hydraulic fluid under pressuretherefrom.
 3. The tractor of claim 2 wherein said hydrostatic motor isengaged with an output gear set to transfer rotational power from saidhydrostatic motor to both said front and rear axle assemblies.
 4. In adrive mechanism for a tractor having a chassis supported by a front axleassembly and a rear axle assembly, and an engine for providing operativepower for said tractor, a splitter gearbox comprising: a power inputshaft delivering rotational power to said splitter gearbox from saidengine; a hydrostatic pump mechanically operatively connected to saidpower input shaft to receive rotational power therefrom for powering thefront and rear axle assemblies; a hydrostatic motor mounted on saidsplitter gearbox in flow communication with said hydrostatic pump toreceive operative power therefrom; and an output shaft mounted in saidsplitter gearbox in mechanical communication with said front and rearaxle assemblies to effect a driving connection therewith for the purposeof delivering traction power thereto.
 5. The drive mechanism of claim 4wherein said splitter gearbox further includes an input gear setassociated with said hydrostatic pump to transfer rotational power fromsaid input shaft to said hydrostatic pump and an output gear setassociated with said hydrostatic motor to transfer rotational powergenerated by said hydrostatic motor to said output shaft, said input andoutput gear sets sharing a common lubrication sump.
 6. The drivemechanism of claim 5 wherein said input gear set includes a PTO drivegear for driving a PTO shaft that extends out of said splitter gearboxfor remote access thereto.
 7. The drive mechanism of claim 6 whereinsaid splitter gearbox is mounted to said rear axle assembly to share acommon lubrication sump therewith.
 8. In a tractor having a chassissupported by a front axle assembly and a rear axle assembly, and anengine for providing operative power for said tractor, the improvementcomprising: a splitter gearbox mounted to said rear axle assembly toshare a common oil sump therewith, said splitter gearbox beingoperatively connected to said engine to receive rotational powertherefrom and being operatively connected to said front and rear axleassemblies to deliver rotational power thereto, said splitter gearboxincluding: a power input shaft delivering rotational power to saidsplitter gearbox from said engine; a hydrostatic pump mechanicallyoperatively connected to said power input shaft to receive rotationalpower therefrom for powering the front and rear axle assemblies; ahydrostatic motor mounted on said splitter gearbox in flow communicationwith said hydrostatic pump to receive operative power therefrom; and anoutput shaft mounted in said splitter gearbox in mechanicalcommunication with said front and rear axle assemblies to effect adriving connection therewith for the purpose of delivering tractionpower thereto.
 9. The tractor of claim 8 wherein said splitter gearboxfurther includes: an input gear set associated with said hydrostaticpump to transfer rotational power from said input shaft to saidhydrostatic pump; and an output gear set associated with saidhydrostatic motor to transfer rotational power generated by saidhydrostatic motor to said output shaft, said input and output gear setssharing a common lubrication sump.
 10. The tractor of claim 9 whereinsaid input gear set includes a PTO drive gear for driving a PTO shaftthat extends out of said splitter gearbox for remote access thereto. 11.The tractor of claim 10 wherein said input gear set also drives ahydraulic pump for powering a hydraulic system of said tractor.
 12. Thetractor of claim 11 wherein said input gear set includes a drive gearconnected to said hydrostatic pump for effecting rotation thereof, saiddrive gear also being connected to said hydraulic pump for simultaneousoperation of both said hydrostatic pump and said hydraulic pump.
 13. Ina tractor having a chassis supported by a front axle assembly and a rearaxle assembly, and an engine for providing operative power for saidtractor, the improvement comprising: a splitter gearbox supported onsaid chassis and being operatively connected to said engine to receiverotational power therefrom and being operatively connected to said frontand rear axle assemblies to deliver rotational power thereto, saidsplitter gearbox including: a power input shaft delivering rotationalpower to said splitter gearbox from said engine; a hydrostatic pumpmechanically operatively connected to said power input shaft to receiverotational power therefrom for powering the front and rear axleassemblies; a hydrostatic motor mounted on said splitter gearbox in flowcommunication with said hydrostatic pump to receive operative powertherefrom; and an output shaft mounted in said splitter gearbox andextending both fore and aft of said splitter gearbox to be operativelycoupled simultaneously in mechanical communication with both said frontaxle assembly and said rear axle assembly to effect a driving connectiontherewith for the purpose of delivering traction power thereto.
 14. Thetractor of claim 13 wherein said splitter gearbox further includes: aninput gear set associated with said hydrostatic pump to transferrotational power from said input shaft to said hydrostatic pump; and anoutput gear set associated with said hydrostatic motor to transferrotational power generated by said hydrostatic motor, said output gearset including a driven gear rotatably driven from said hydrostaticmotor, said output shaft being affixed to said driven gear for rotationtherewith.
 15. The tractor of claim 14 wherein said driven gear ismounted on a central portion of said output shaft located within saidsplitter gearbox, said output shaft extending fore-and-aft from saiddriven gear.